Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/62—Record carriers characterised by the selection of the material
  • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
  • G11B5/739—Magnetic recording media substrates
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
  • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C19/00—Surface treatment of glass, not in the form of fibres or filaments, by mechanical means
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
  • C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
  • C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C23/00—Other surface treatment of glass not in the form of fibres or filaments
  • C03C23/0075—Cleaning of glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/095—Glass compositions containing silica with 40% to 90% silica, by weight containing rare earths
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/097—Glass compositions containing silica with 40% to 90% silica, by weight containing phosphorus, niobium or tantalum
• • G11B5/7315—
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
  • G11B5/82—Disk carriers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
  • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24273—Structurally defined web or sheet [e.g., overall dimension, etc.] including aperture
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31—Surface property or characteristic of web, sheet or block
  • Y10T428/315—Surface modified glass [e.g., tempered, strengthened, etc.]

Definitions

• the present invention relates to glass used as a substrate for an information recording medium such as a magnetic disk, an information recording medium substrate made of the glass, an information recording medium comprising the substrate, and methods for producing them.
• a magnetic storage device such as a computer
• a magnetic recording medium As magnetic recording media, flexible disks and hard disks are known.
• substrate materials for hard disks there are, for example, aluminum substrates, glass substrates, ceramic substrates, carbon substrates and the like. Practically, depending on the size and application, mainly aluminum substrates and Glass substrate is used.
• perpendicular magnetic recording system In recent years, in order to further increase the recording density of information recording media (for example, 100 Gbit Z High recording density of 2 inches or more), perpendicular magnetic recording system is adopted. The recording density can be greatly improved by adopting the perpendicular magnetic recording system.
• the distance between the head for writing / reading data for example, a magnetic head
• the surface of the medium called flying height in the case of magnetic recording media
• flying height In the case of magnetic recording media, it is necessary to let However, if the smoothness of the substrate surface is low, the unevenness of the substrate surface is reflected on the medium surface, and the distance between the head and the medium surface cannot be reduced, which hinders the improvement of the linear recording density.
• the roughness of the main surface of the substrate is very strict, such as 0.25 nm or less, and is required.
• the track density in addition to the linear recording density.
• data is recorded and read along the rotation direction while rotating the medium at a high speed around the central axis and slightly changing the distance from the central axis.
• the above-mentioned linear recording density is an index of how much data can be recorded per unit length in the rotation direction.
• the track density corresponds to the recording density in the radial direction of the medium.
• a position for recording data is assigned in advance according to the distance from the center axis. However, in a medium having a high track density, a slight deviation in the distance causes an error.
• the center hole for mounting the rotating shaft for rotating the medium must be precisely formed in the center of the substrate, and the inner diameter dimension tolerance of the hole must be small.
• inner diameter dimensional errors in magnetic disks are severe, and there are other reasons why accuracy control is required. This is because the dimensional error force S on the inner peripheral surface of the air disk directly affects the installation accuracy when the magnetic disk is fitted to the HDD spindle motor. If the inner diameter error is large, there is a possibility of inducing a mechanical error in the stacking servo (writing servo information to the magnetic disk) that is performed before the magnetic disk is assembled in a magnetic disk device such as an HDD.
• the mating with the spindle at the time of tucking may cause a malfunction. If such a problem occurs, data cannot be recorded and played back.
• the distance between tracks on a magnetic disk has become narrower as the recording density of information has increased. Specifically, for example, when the track-to-track distance (light track) is narrower, such as 0.2 xm or less, the information recording track is shifted by a slight shift of the substrate. The result is that it cannot be read correctly.
• the current inner diameter tolerance standard is within 20.025 mm ⁇ 0.025 mm for ⁇ 65 mm (65 mm diameter) substrates and within 12.025 mm ⁇ 0.025 mm for ⁇ 48 mm substrates.
• a glass substrate for an information recording medium may be chemically strengthened so as not to be damaged when the information recording medium is manufactured or when the medium is incorporated into an information recording apparatus.
• glass containing an alkali component is generally immersed in a molten salt containing an alkali having an ionic radius larger than that of the alkali component, and ion exchange between alkali ions on the substrate surface and Al force reion in the molten salt is performed.
• a compressive stress layer is formed on the substrate surface.
• a large number of substrates are immersed in the molten salt one after another for ion exchange.
• the stress distribution formed by chemical strengthening is slightly different between the substrate that was chemically strengthened initially and the substrate that was chemically strengthened using a molten salt after processing a large number of sheets even if the processing conditions were constant.
• the glass substrate undergoes a slight dimensional change before and after the strengthening process due to internal stress formed by chemical strengthening. For this reason, the dimensional change also varies between substrates having slightly different stress distributions. If such variation in dimensional change occurs, the position of the center hole may slightly shift in each substrate, or the inner diameter dimensional tolerance of the center hole may increase.
• the alkali metal ions may be eluted from the glass substrate.
• the alkali metal ions move to the surface during the heating process when the magnetic film is formed and are eluted, or the magnetic film is eroded. There is a problem that the adhesion strength of the magnetic film is deteriorated.
• a first object of the present invention is to provide a glass for use in an information recording medium substrate having both excellent acid resistance and alkali resistance, and an information recording medium glass substrate composed of the glass. It is to provide.
• a second object of the present invention is composed of glass for use in a substrate for an information recording medium capable of imparting excellent impact resistance by chemical strengthening with little alkali metal component elution, and the glass. It is to provide a glass substrate for an information recording medium.
• a third object of the present invention is to make it possible to realize an information recording medium substrate having an extremely smooth surface and an extremely clean surface, and a glass substrate for an information recording medium composed of the glass. Is to provide.
• a fourth object of the present invention is to provide a glass capable of producing a substrate for an information recording medium having excellent surface smoothness even after cleaning with high chemical durability.
• Another object of the present invention is to provide a glass substrate material having high shape stability after chemical strengthening treatment.
• An object of the present invention is to provide a method for manufacturing the glass substrate for each information recording medium, an information recording medium provided with the glass substrate, and a method for manufacturing the information recording medium.
• the present invention provides:
• Glass I glass for use in information recording media substrates
• the glass has a SiO content of 60 mol% or more, and SiO and A
• the total content of 10 is 75 mol% or more.
• the glass has a total content of CaO and MgO higher than that of SrO and BaO when expressed in mol%.
• the glass comprises, in mol%, SiO: 50 to 75%, A1 0: 3 to 15%, L
• Another aspect of the present invention provides:
• A10 is 3-15%
• the mol ratio of the total content of Li ⁇ , Na ⁇ and K ⁇ ⁇ ⁇ ⁇ to the total content of SiO, A10 and ZrO ((Li O + Na O + KO) / (Si ⁇ + A1 ⁇ + ZrO)) is 0.28 or less ,
• the glass II used for the board
• a further aspect of the present invention provides:
• the content of SiO is 50 mol% or more, the total content of SiO and A10 is 70 mol% or more, the total content of the alkali metal oxide and the alkaline earth metal oxide is 8 mol% or more,
• glass III used for the substrate for information recording media which is.
• the glass has a SiO content of 60 mol% or more, and SiO and A1
• the total content of ⁇ is 75 mol% or more.
• the glass contains at least one of LiO and NaO, and the total content of iO and NaO is less than 24 mol%.
• the glass has a total content of Li 0 and Na 0 of 22 mol% or less.
• the glass is expressed in terms of mol: SiO: 60 to 75%, A10: 3 to 15%, Zr
• a further aspect of the present invention provides:
• One or more alkali metal oxides selected from the group consisting of Li 0, Na 0 and K ⁇ ;
• One or more alkaline earth metal oxides selected from the group consisting of MgO, CaO, SrO and BaO, and ZrO, HfO, NbO, TaO, LaO, YO and TiO force One or more oxides selected from the group,
• the total content of Li 0 and Na 0 is 10-22 mol%
• the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO is more than 0 mol% and less than 4 mol%
• Glass IV Aluminosilicate glass for chemical strengthening
• the glass has a SiO content of 50 mol% or more and a total content of SiO and A10 is 70 mol% or more.
• the glass has a total content of SiO and A10 of 75 mol% or more.
• the glass comprises ZrO, HfO, Nb0, TaO, La0, Y0 and the total content of Li0, Na0, K0, MgO, CaO, SrO and BaO.
• Mol ratio of total content of TiO ((ZrO + HfO + Nb 0 + Ta O + La O + YO + ⁇ ) / (Li O + Na O
• the glass comprises, in mol%, A1 0 3% or more, LiO, Na 0, K
• MgO, CaO, SrO and BaO total 8% or more, MgO, CaO, SrO and BaO in total include more than 0% and 5% or less.
• a further aspect of the present invention provides:
• One or more alkali earth metal oxides, ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO One or more oxides selected from the group,
• glass V glass V
• the glass has a SiO content of 50 mol% or more and a total content of SiO and A10 is 70 mol% or more.
• the glass has a total content of SiO and A10 of 75 mol% or more.
• the glass has a total content power of S8mol% or more of the alkali metal oxide and the alkaline earth metal oxide, and a total of the alkali metal oxide and the alkaline earth metal oxide.
• the glass contains at least one of Li 0 and Na 0,
• the total content of 10 and Na 0 is 24 mol% or less.
• the glass has a total content of Li 0 and Na 0 of 22 mol% or less.
• the glass is expressed in terms of mol: SiO 60 75% A1 0 3 15% Zr
• Hf ⁇ Nb ⁇ Ta ⁇ La ⁇ Y ⁇ and Ti ⁇ contain a total of 0.34%.
• a further aspect of the present invention provides:
• A10 is 5 20%, but the total amount of SiO and A10 is 74% or more,
• Li ⁇ exceeds 1% and below 9%
• CaO exceeds 0% and 5% or less. However, the total amount of MgO and CaO is 5% or less, and the content of CaO is larger than the content of MgO.
• Glass VI Glass for use in information recording media substrates (hereinafter referred to as “Glass VI”);
• A10 is 5-20%, but the total amount of SiO and A10 is 74% or more,
• ZrO exceeds 0% and 5.5% or less
• Li ⁇ exceeds 1% and below 9%
• CaO exceeds 0% and 5% or less. However, the total amount of MgO and CaO is 5% or less, and the content of CaO is larger than the content of MgO.
• glass VII for use in an information recording medium substrate
• the glass has a total content of SiO and A10 exceeding 79%.
• the glass contains 11% or more of A10.
• the glass contains 0.1 to 4% MgO.
• the glass comprises SiO, A10, ZrO, LiO, NaO, KO, MgO and
• the total content of CaO is 9% or more.
• each of the aforementioned glasses may further contain Fe.
• a further aspect of the present invention relates to a chemically tempered glass for use in an information recording medium substrate obtained by subjecting the glass to a chemical tempering treatment.
• a further aspect of the present invention relates to a glass substrate for an information recording medium composed of the glass.
• the glass substrate has a main surface roughness Ra of less than 0.25 nm.
• the glass substrate is subjected to a chemical strengthening treatment.
• the glass substrate has a bending strength of 10 kg or more.
• the glass substrate has a thickness of 1 mm or less.
• the glass substrate has a thickness power of .3 mm or more.
• the glass substrate may be disk-shaped and have an opening in the center.
• a further aspect of the present invention provides:
• a method of manufacturing a glass substrate for an information recording medium comprising: a step of mirror polishing the glass; and a cleaning step of performing acid cleaning and alkali cleaning after mirror finishing
• the manufacturing method further includes performing a chemical strengthening treatment between the polishing step and the cleaning step.
• the acid cleaning and the alkali cleaning are successively performed.
• alkali cleaning is performed after the acid cleaning.
• a further aspect of the present invention relates to an information recording medium having an information recording layer on the glass substrate for information recording medium.
• the information recording medium is a perpendicular magnetic recording magnetic recording medium.
• the information recording medium includes a soft magnetic underlayer, an amorphous underlayer, a crystalline underlayer, a perpendicular magnetic recording layer, a protective layer, and a lubricating layer in this order on the substrate.
• the information recording medium has a recording density force of Sl30 Gbit / inch 2 or more.
• a further aspect of the present invention relates to a method for producing an information recording medium, wherein a glass substrate for information recording medium is produced by the above method and an information recording layer is formed on the glass substrate.
• glass for use in an information recording medium substrate having both excellent acid resistance and alkali resistance an information recording medium glass substrate composed of the glass, and the glass substrate.
• glass for use in an information recording medium substrate capable of imparting excellent impact resistance by chemical strengthening with little alkali metal component elution and an information recording medium composed of the glass Glass substrate and manufacturing method thereof, and an information recording medium including the substrate and manufacturing method thereof can be provided.
• the glass capable of realizing a substrate for an information recording medium having an extremely smooth surface and a very clean surface, a glass substrate for an information recording medium composed of the glass, and a method for producing the same,
• the ability to provide an information recording medium with a substrate and a method for manufacturing the same is possible.
• a glass having excellent surface smoothness that can cope with high recording density such that the distance between tracks is 0.2 zm or less, more preferably 0.15 zm or less, and further preferably 0.12 zm or less.
• An information recording medium substrate manufactured and a manufacturing method thereof, and an information recording medium including the substrate and a manufacturing method thereof can be provided.
• the present invention relates to glass for use in an information recording medium substrate.
• Glasses to be used for the information recording medium substrate of the present invention (hereinafter also referred to as “information recording medium substrate glass”) are roughly classified into the above-mentioned glasses I to VII. Hereinafter, these glasses will be described in detail.
• CaO and MgO in total 1 to 6%, but CaO content is higher than MgO content, ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO in total 0% Over 4%, including Mol ratio of the total content of Li 0, Na O and KO to the total content of SiO, Al O, ZrO, HfO, Nb O, Ta O, La O, YO and ⁇ ((Li O + Na O + K ⁇ ) / (SiO
• Glass I it is possible to provide a substrate for an information recording medium excellent in both acid resistance and alkali resistance.
• Glass I the content of each component and the total content are expressed by mol%, and the ratio between the contents is expressed by mol ratio.
• Glass I is an oxide glass, and the content of each component is shown as a value converted to an oxide.
• SiO is a glass network-forming component, and it is essential to improve glass stability, chemical durability, especially acid resistance, reduce thermal diffusion of the substrate, and increase the heating efficiency of the substrate by radiation. It is an ingredient.
• A10 also contributes to the formation of a glass network, and functions to improve glass stability and chemical durability.
• the total content of SiO and Al 0 is 70% or more, preferably 74% or more, more preferably 75% or more, in order to improve chemical durability, particularly acid resistance.
• the total content of SiO and Al 0 is 85% or less, preferably 80% or less.
• the content of SiO is 50% or more, preferably 55% or more, more preferably 60% or more, still more preferably 63% or more, more preferably 65% or more. And. However, if SiO is introduced excessively, undissolved material is generated in the glass. Therefore, it is preferable to reduce the SiO content to 75% or less, more preferably 72% or less, and more preferably 70% or less. Even better.
• a substrate is prepared by covering glass containing undissolved material, a part of the undissolved material may be exposed on the substrate surface to form protrusions. A substrate having such protrusions cannot be used as a substrate for an information recording medium that requires high smoothness. Therefore, the meltability of the glass used for the information recording medium substrate is an important characteristic.
• the content of A10 is 3% or more, preferably 5% or more, more preferably 7% or more.
• Li 0, Na 2 O and KO not only improve meltability and moldability, but also increase the thermal expansion coefficient to give thermal expansion characteristics suitable for information recording media substrates, particularly magnetic recording media substrates. This is a useful component.
• Li 0 and Na 0 are components responsible for ion exchange during chemical strengthening when used as chemically strengthened glass. In order to obtain these effects, the total content of Li 0, Na 0 and K 0 should be 10% or more. However, when the amount of alkali metal oxide is excessive, chemical durability, particularly acid resistance, tends to decrease.
• the upper limit of the total content of LiO, NaO, and KO is set to SiO, A10, ZrO, HfO, NbO, TaO, Determined in relation to the total content of La ⁇ , ⁇ and Ti ⁇ . Details thereof will be described later.
• the total content of LiO, NaO and K K be 22% or less.
• Li 0 and Na 0 as glass components in order to obtain an effect of reducing and preventing elution of alkali metal components by the mixed alkali effect.
• the preferred lower limit of the content of Li 0 is 5%, more preferably the lower limit is 6%, the still more preferred lower limit is 7%, the preferred upper limit is 15%, and the more preferred upper limit. Is 13%, and a more preferred upper limit is 10%.
• a preferred lower limit for the content of Na 0 is 5%, a more preferred lower limit is 7%, a still more preferred lower limit is 10%, a preferred upper limit is 15%, and a more preferred upper limit is 13%.
• the glass components that directly contribute to ion exchange during chemical strengthening are Li 0 and Na 0, which contribute to ion exchange in the molten salt.
• Some alkali ions are Na ions and / or K ions.
• the Li ion concentration in the molten salt increases, but a large amount of glass with a mol ratio of Li 0 to Na 0 (Li O / Na O) exceeding 1.04 is processed.
• the concentration of Li ions in the molten salt increases significantly, and the balance between alkali ions that contribute to ion exchange and alkali ions that do not contribute to ion exchange changes significantly from the beginning of the treatment.
• the processing conditions optimized at the start of processing deviate from the optimal range as the number of processed sheets increases, and as described above, the substrate varies in shape. This may cause a large inner diameter dimensional tolerance of the center hole of the substrate, and may cause problems such as insufficient formation of the compressive stress layer and waviness of the substrate.
• Li 0 to Na 0 Li O / Na 0
• K 2 O is an optional component that functions to increase the meltability and increase the thermal expansion coefficient.
• a preferable range of the K 0 content is 0 to 3%, a more preferable range is 0 to 2%, and a further preferable range is 0 to 1%.
• Introducing a small amount of K 0 has the effect of reducing the variation in the compressive stress layer between substrates when chemically strengthening a large number of substrates, so introducing 0.1% or more is preferable within the above range. More preferably.
• CaO and MgO serve to improve meltability, formability and glass stability, increase rigidity and hardness, and increase the thermal expansion coefficient. However, the chemical durability is lowered by excessive introduction, so the total content of CaO and MgO is 1-6%.
• a preferable lower limit of the total content of CaO and MgO is 1.5%, a more preferable lower limit is 2%, a preferable upper limit is 5.5%, a more preferable upper limit is 5%, and a further preferable upper limit is 4%.
• CaO and MgO have the function of reducing the ion exchange speed during chemical strengthening.
• the devitrification resistance is further improved and the chemical durability is enhanced, and therefore, the content of CaO is made larger than the content of MgO.
• the preferred content of CaO is more than 0.5% and not more than 5%.
• the more preferred lower limit of the CaO content is 0.8%, the still more preferred lower limit is 1%, the more preferred upper limit is 4%, and the more preferred upper limit is Three %.
• the preferred MgO content is 0% or more and less than 3%.
• the preferred lower limit of the MgO content is 0.1%, the more preferred lower limit is 0.3%, and the more preferred lower limit is 0.5.
• a preferred upper limit is 2.5%, more preferably 2%.
• the MgO content may be determined by determining the mol ratio (MgO / CaO) within the above-mentioned preferable range after determining the CaO content and determining the CaO content, the mol ratio, and the force.
• alkaline earth metal oxides SrO and BaO also have the function of improving the meltability and increasing the coefficient of thermal expansion.
• the addition of SrO and BaO tends to lower the chemical durability, increase the specific gravity of the glass, and increase the raw material cost. Therefore, it is preferable to make the total content of CaO and MgO higher than the total content of SrO and BaO.
• the total content of SrO and BaO is preferably 0 to 5%, more preferably 0 to 2%, and still more preferably 0 to 1%.
• a preferable range of the SrO content is 0 to 2%, and a more preferable range is 0 to 1%, and it is even more preferable not to introduce SrO.
• a preferable range of the content of BaO is 0 to 2%, and a more preferable range is 0 to 1%, and it is further preferable not to introduce BaO.
• ZrO, HfO, Nb0, Ta0, La0, Y0 and TiO function to improve chemical durability, particularly alkali resistance.
• meltability deteriorates due to excessive introduction. Therefore, from the viewpoint of improving chemical durability, especially alkali resistance, while maintaining meltability,
• the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO is more than 0% and less than 4%.
• the preferred lower limit of the total content is 0.3%, the more preferred lower limit is 0.5%, the still more preferred lower limit is 0.7%, the preferred upper limit is 3%, the more preferred upper limit is 2%, and the more preferred upper limit is 1.5%. .
• the relationship between the amount and the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO is preferably in the following range.
• the mol ratio is preferably 0.18 or less, more preferably 0.15 or less. It is more preferable to set it to 0.13 or less. It is even more preferable to set it to 0.12 or less.
• the content of TiO is preferably 0-2%, more preferably 0-1%.
• HfO, Nb 0, Ta 0 and La O increase the specific gravity of the glass and increase the weight of the substrate. It is preferable to set the content in the range of 0 to 2%. It is more preferable to set the content in the range of 0 to 1%.
• NbO, TaO and LaO are not introduced.
• the preferred contents of HfO, NbO, TaO and La O are 0 to 2%, more preferably 0 to 1%, and HfO, NbO, TaO and La O are not introduced. More preferably.
• Y 0 maintains the glass stability and obtains the above desired effect.
• a range of ⁇ 2% is preferred.
• a range of 0-1% is more preferred. It ’s even better to introduce Y 0.
• ZrO While maintaining glass stability, ZrO has a function of improving chemical durability, in particular, alkali resistance, and increases rigidity and toughness, and has a function of increasing the efficiency of chemical strengthening.
• the raw material cost is lower than Y 0, the mol ratio of ZrO content to the total content of ZrO, HfO, Nb 0, Ta 0, La 0, YO and TiO (ZrO / (ZrO + HfO + Nb
• O + Ta O + La O + YO + TiO) is preferably in the range of 0.5 to 1, more preferably in the range of 0 ⁇ 8 to 1, more preferably in the range of 0.9 to 1. It is particularly preferable that the range of 0.95 to 1 is even more preferable.
• the ZrO content is preferably 0.3% or more, more preferably 0.5% or more. More preferably, it is 0.7% or more.
• the ZrO content is preferably 4% or less, more preferably 3% or less, and even more preferably 2% or less. Further preferably, it is more preferably 1.5% or less.
• Glass I may be added with a clarifying agent such as Sb0, SnO, or CeO as necessary.
• a clarifying agent such as Sb0, SnO, or CeO
• Sb0 is preferable.
• Addition of SnO and CeO is preferable Addition of SnO is more preferable
• SiO is 50 to 75%
• Glass II it is possible to provide a substrate for an information recording medium excellent in both acid resistance and alkali resistance.
• Glass II the content of each component and the total content are expressed by mol%, and the ratio between the contents is expressed by mol ratio.
• Glass II is an oxide glass, and the content of each component is shown as a value converted to an oxide.
• SiO is a glass network-forming component, and it is essential to improve glass stability, chemical durability, especially acid resistance, lower the thermal diffusion of the substrate, and increase the heating efficiency of the substrate by radiation. It is an ingredient. From the viewpoint of improving the glass stability, the SiO content is 50% or more, preferably 55% or more, more preferably 60. / o or more, more preferably 63% or more, and even more preferably 65% or more. However, if SiO is introduced excessively, undissolved material is generated in the glass. Therefore, the SiO content is 75% or less, but it is preferably 72% or less, and preferably 70% or less.
• A10 also contributes to the formation of a glass network, and functions to improve glass stability and chemical durability.
• the content of A10 is 3% or more, preferably 5% or more, and more preferably 7% or more.
• the content of A10 is made 15% or less. Preferably it is 12% or less.
• the total content of SiO and A10 is preferably 70% or more, more preferably 74% or more. More preferably, it is 75% or more. In consideration of the meltability of the glass, the total content of SiO and A10 is preferably 85% or less, more preferably 80% or less.
• LiO, Na0, and K0 improve the meltability and formability as well as the thermal expansion coefficient.
• Li 0 and Na 0 are components responsible for ion exchange during chemical strengthening when used as chemically strengthened glass.
• the Li 0 content is 5 to 15%
• the Na 0 content is 5 to 15%
• the K 0 content is 0 to 3%.
• a preferred lower limit for the Li 0 content is 6%
• a more preferred lower limit is 7%
• a preferred upper limit is 13%
• a more preferred upper limit is 10%.
• the preferable lower limit of the NaO content is 7%, the more preferable lower limit is 10%, and the preferable upper limit is 13%.
• the glass components that directly contribute to ion exchange during crystallization are Li 0 and Na 0.
• Some alkali ions that contribute to the exchange are Na ions and / or K ions.
• the concentration of Li ions in the molten salt increases, but a large amount of glass with a molar ratio of Li 0 to Na 0 (Li O / Na 0) exceeding 1.04 is processed.
• the concentration of Li ions in the molten salt increases significantly, and the balance between alkali ions that contribute to ion exchange and alkali ions that do not contribute to ion exchange changes significantly from the beginning of the treatment.
• the processing conditions optimized at the start of processing deviate from the optimal range as the number of processed sheets increases, and as described above, the shape varies depending on the substrate, and the inner diameter dimensional tolerance of the center hole of the substrate.
• there may be problems such as insufficient formation of the compressive stress layer and waviness of the substrate.
• K 2 O is an optional component that functions to increase the meltability and increase the thermal expansion coefficient as described above.
• the content of K0 is 0 to 3%, but a preferred range is 0 to 2%, and a more preferred range is 0 to
• the upper limit of the total content of Li 0, Na 0 and K 0 is determined in relation to the total content of SiO, A10 and ZrO. Details thereof will be described later.
• the total content of Li 0, Na 0 and K 0 is preferably 22% or less, more preferably 21.5% or less, and more preferably 21% or less. More preferably, it is more preferably 20% or less.
• CaO and MgO work to improve meltability, formability and glass stability, increase rigidity and hardness, and increase the thermal expansion coefficient.
• CaO is excellent in improving the meltability, formability, and glass stability.
• the CaO content should be more than 0.5% and not more than 5%.
• the preferable lower limit of the CaO content is 0.8%, the more preferable lower limit is 1%, the preferable upper limit is 4%, and the more preferable upper limit is 3%.
• the MgO content is 0% or more and less than 3%.
• the preferred lower limit of the MgO content is 0.1%, the more preferred lower limit is 0.3%, and the more preferred lower limit is 0.5.
• the preferred upper limit is 2.5%, more preferably 2%.
• the devitrification resistance is further improved and the chemical durability is enhanced, so that the CaO content is higher than the MgO content.
• the MgO content may be determined by determining the mol ratio (MgO / CaO) within the above preferred range after determining the CaO content, and determining the CaO content, the mol ratio, and the force.
• the total content of CaO and MgO is preferably 1 to 6%. Les.
• a preferred lower limit of the total content of CaO and MgO is 1.5%, a more preferred lower limit is 2%, a preferred upper limit is 5.5%, a more preferred upper limit is 5%, and a further preferred upper limit is 4%.
• CaO and MgO have the function of reducing the ion exchange speed during chemical strengthening. Therefore, when chemically strengthening a substrate composed of glass with appropriate amounts of these components and mass-producing chemically strengthened glass substrates, it is possible to suppress an increase in the inner and outer diameter tolerances of the substrate caused by excessive chemical strengthening. it can.
• alkaline earth metal oxides SrO and BaO also have the function of improving the meltability and increasing the coefficient of thermal expansion.
• the addition of SrO and BaO tends to lower the chemical durability, increase the specific gravity of the glass, and increase the raw material cost. Therefore, it is preferable to make the total content of CaO and MgO higher than the total content of SrO and BaO.
• the total content of SrO and BaO is preferably 0 to 5%, more preferably 0 to 2%, and still more preferably 0 to 1%.
• the preferable range of the SrO content is 0 to 2%, and the more preferable range is 0 to 1%, and it is more preferable not to introduce SrO.
• a preferable range of the content of BaO is 0 to 2%, and a more preferable range is 0 to 1%, and it is further preferable not to introduce BaO.
• ZrO has a function of improving chemical durability, particularly alkali resistance, while maintaining glass stability, and has a function of increasing rigidity and toughness, and a function of improving chemical strengthening efficiency.
• meltability deteriorates due to excessive introduction. Therefore, in order to improve chemical durability, particularly alkali resistance, while maintaining meltability, the ZrO content is set to 0.3 to 4%.
• the preferred lower limit for the 0 content is 0.5%, the more preferred lower limit is 0.7%, the preferred upper limit is 3%, the more preferred upper limit is 2%, and the still more preferred upper limit is 1.5%.
• the upper limit of (SiO + A1 ⁇ + ZrO)) should be 0.28 or less.
• a preferable range of the mol ratio is 0.27 or less, and a more preferable range is 0.26 or less.
• a preferable lower limit of the mol ratio is 0.1, a more preferable lower limit is 0.15, and a further preferable lower limit is 0.2.
• a clarifying agent such as Sb 0, SnO, or CeO may be added to Glass II as necessary.
• Sb 0 is not preferable.
• Addition of CeO is preferable.
• Addition of SnO is more preferable.
• SiO, Al O, Li 0, Na O, and K 2 O forces are one or more selected alkalis
• the SiO content is 50 mol% or more, and the total content of SiO and Al 0 is 70 mol% or more.
• the total content of the alkali metal oxide and the alkaline earth metal oxide is 8 mol% or more
• Glass III it is possible to provide a substrate for an information recording medium excellent in both acid resistance and alkali resistance.
• Glass III is an oxide glass, and the content of each component is shown as a value converted to an oxide.
• SiO is a network-forming component of glass, and has glass stability, chemical durability,
• A10 also contributes to the formation of glass networks and improves glass stability and chemical durability.
• glass m the sum of sio and Ai 0 is added to improve chemical durability, especially acid resistance.
• 2 2 3 Content is 70% or more, preferably 75% or more, more preferably 76% or more. Considering the meltability of glass, it is preferable to keep the total content of SiO and Al 0 to 85% or less. 80% or less
• the SiO content is 50% or more, preferably 60% or more, More preferably, it is 63% or more, and further preferably 65% or more.
• the SiO content is preferably 75% or less, more preferably 72% or less, and more preferably 70% or less. More preferably.
• a preferred range for the content of A10 is 3% or more, a more preferred range is 5% or more, and a further preferred range is 7% or more. However, if A10 is introduced excessively, the meltability of the glass is lowered. Therefore, the content of A10 is preferably 15% or less, more preferably 12% or less.
• glass III contains a relatively large amount of SiO and A10 in total.
• it is selected from the group consisting of one or more alkali metal oxides selected from the group consisting of LiO, NaO and KO, and MgO, CaO, SrO and BaO.
• alkali metal oxides and alkaline earth metal oxides can improve the meltability of the glass and make the thermal expansion characteristics within a range suitable for the substrate for information recording media.
• the chemical durability tends to decrease.
• the total content of CaO, SrO and BaO is preferably 24% or less. From the viewpoint of improving the meltability and increasing the coefficient of thermal expansion, the preferable range of the total content is 10% or more, more preferably 15% or more, and still more preferably 20% or more.
• ZrO, HfO, Nb0, Ta0, La0, Y0, and TiO function to improve chemical durability, particularly alkali resistance.
• meltability deteriorates due to excessive introduction. Therefore
• the mol ratio is 0.040 or more. If the mol ratio is excessive, the meltability tends to decrease or the glass stability tends to decrease.Therefore, the mol ratio is preferably 0.18 or less, and more preferably 0.15 or less. It is even more preferable to make it below 0.15 or less.
• the total content of ZrO, HfO, NbO, TaO, LaO, YO and TiO 0.3% or more. It is more preferable to make it 0.5% or more 0.7. More preferably, it is at least 0 .
• the total content is preferably 4% or less, more preferably 3% or less, and even more preferably 2% or less. More preferably, it is more preferably 1.5% or less.
• a preferred embodiment of Glass III contains at least one of Li 0 and Na 0 and Li 0 and
• This glass has a total Na 0 content of 24% or less.
• Li 0 and Na 0 are components that further improve the meltability.
• Li 0 and Na 0 are important components when chemically strengthening glass III. Furthermore, it has a strong function of imparting suitable thermal expansion characteristics to an information recording medium substrate, particularly a magnetic recording medium substrate, by increasing the thermal expansion coefficient.
• Li 0 and Na 0 as a glass component, which reduces the elution of the alkali metal component due to the mixed alkali effect and enhances the prevention effect.
• MgO functions to improve the meltability, rigidity and hardness and to increase the thermal expansion coefficient.
• the content is preferably 0% or more and less than 5%.
• a preferred lower limit of the MgO content is 0.1%, a more preferred lower limit is 0.3%, and a more preferred lower limit is 0.5%. Further, the MgO content is preferably less than 3%, more preferably 2% or less.
• CaO works to improve the devitrification resistance by improving the meltability, rigidity and hardness, increasing the thermal expansion coefficient, and introducing an appropriate amount. Furthermore, like MgO, it also functions to control the ion exchange speed during chemical strengthening. However, since the chemical durability decreases due to excessive introduction, the content is preferably 0 to 5%. A more preferable lower limit of the CaO content is 0.1%, a further preferable lower limit is 0.5%, a more preferable upper limit is 4%, and a further preferable upper limit is 3%.
• the glass III like the glass I, it is preferable that the content of CaO is larger than the content of MgO in order to further improve the devitrification resistance and the chemical durability.
• the glass II also has the same molar ratio of MgO to CaO (MgO / CaO) as in Glass I. A range of 97 is preferable. A range of 0.4 to 0 ⁇ 97 is more preferable.
• a preferred lower limit of the total content of MgO and CaO is 1.5%, a more preferred lower limit is 2%, a preferred upper limit is 5.5%, a more preferred upper limit is 5%, and a further preferred upper limit is 4%.
• SrO and BaO also have the function of improving the meltability and increasing the thermal expansion coefficient.
• the addition of SrO and BaO tends to lower the chemical durability, increase the specific gravity of the glass, and increase the raw material cost. Therefore, the total content of SrO and BaO is preferably 0 to 5%, more preferably 0 to 2%, and still more preferably 0 to 1%.
• Preferred range of SrO content The range is 0 to 2%, and a more preferable range is 0 to 1%, and it is further preferable not to introduce SrO.
• a preferable range of the content of BaO is 0 to 2%, and a more preferable range is 0 to 1%, and it is more preferable not to introduce BaO.
• a more preferable embodiment of the glass bottle is that in terms of mol, SiO is 60 to 7
• glass containing 3 to 15% A10 and 0.3 to 4% ZrO, and a more preferable embodiment has the above composition, and further includes ZrO, HfO, NbO, Ta0, LaO and TiO. Glass containing 0.3 to 4% in total,
• a more preferred embodiment is a glass in which the amount of each component of alkali metal oxide and alkaline earth metal oxide is distributed as described above.
• a clarifying agent such as SbO, SnO, or CeO may be added to the glass bottle as necessary.
• One or more alkali metal oxides selected from the group consisting of Li 0, Na 0 and K ⁇ ;
• One or more alkaline earth metal oxides selected from the group consisting of MgO, CaO, SrO and BaO, and a group selected from the group consisting of ZrO, HfO, NbO, TaO, LaO, YO and TiO force Including the above oxides,
• the total content of Li 0 and Na 0 is 10-22 mol%
• the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO is more than 0 mol% and less than 4 mol%
• a chemically strengthened aluminosilicate glass for use in a substrate for an information recording medium.
• Glass IV is a chemically strengthened glass, that is, a glass to which chemical strengthening is applied, and contains at least one of Li 0 and Na 0, preferably both Li 0 and Na 0, necessary for chemical strengthening.
• Glass is an aluminosilicate glass that can reduce and prevent elution of alkali metal ions.
• the total content of Li 0 and Na 0 is limited, and in order not to lower the meltability, at least one alkali selected from the group consisting of MgO, CaO, SrO and BaO forces Introduce earth metal oxides.
• these alkaline earth metal oxides function to hinder ion exchange during chemical strengthening.
• glass IV is selected from the group forces of Zr ⁇ , HfO, Nb 0, Ta 0, La 0 and TiO force that promote ion exchange and improve chemical durability, especially alkali resistance. Introduce at least one oxide. As a result, it is possible to provide a glass that can be chemically strengthened satisfactorily.
• Glass IV is an oxide glass, and the content of each component is shown as a value converted to an oxide.
• Li 0 and Na 0 are components necessary for ion exchange during chemical strengthening, improve the meltability of the glass, and have a thermal expansion coefficient suitable for information recording medium substrates, particularly magnetic recording medium substrates. It is also an effective ingredient in the range.
• the total content of Li 0 and Na 0 is set to 10% or more, and the total content is set to 22% or less from the viewpoint of reducing or preventing alkali metal ion elution.
• the preferred lower limit of the total NaO content is 15%, and the preferred upper limit is 21%. Furthermore, from the viewpoint of reducing and preventing the elution of alkali metal components by the mixed alkali effect, Li 0 and Na
• ZrO, HfO, Nb 0, Ta 0, La 0, ⁇ 0 and TiO function to promote alkali ion exchange during chemical strengthening and to improve chemical durability, particularly alkali resistance. .
• meltability will decrease due to excessive introduction and undissolved matter may be produced.
• the unmelted material is contained in the glass used for the information recording medium substrate, particularly the magnetic recording medium substrate, even if the unmelted material is very small, a part of the unmelted material is present on the substrate surface. It may be exposed to form protrusions and impair the smoothness of the substrate surface.
• the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO is more than 0% and 4% or less.
• the upper limit of the total content is preferably 3%, more preferably 2%, and still more preferably 1.5. / 0 , a preferred lower limit is 0.3%, a more preferred lower limit is 0.5%, and a more preferred lower limit is 0.7%.
• Glass IV contains one or more MgO, CaO, SrO and BaO forces, a group force of them, and an alkaline earth metal oxide selected from them. These components function to maintain meltability and adjust the coefficient of thermal expansion, while preventing ion exchange during chemical strengthening. Therefore, in Glass IV, the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO, which has the function of promoting ion exchange during chemical strengthening and improving chemical durability, Good chemical strengthening is possible by balancing the total content of MgO, CaO, SrO and BaO. Specifically, ZrO, HfO, NbO with respect to the total content of MgO, CaO, SrO and BaO
• LaO + YO + TiO) / (MgO + CaO + SrO + BaO)) is set to 0.015 or more.
• a preferable range of the total content of MgO, CaO, SrO and BaO is more than 0% and 5% or less. When the total amount is 5% or less, chemical strengthening can be performed satisfactorily, and the bending strength of the substrate can be sufficiently improved.
• the preferred lower limit of the total content of MgO, CaO, SrO and BaO is 0.1%, the more preferred lower limit is 0.5%, the more preferred lower limit is 1%, the more preferred range is 1.5%, the more preferred upper limit is 4.5%, and further A preferred upper limit is 4%.
• SiO is a network forming component of glass IV, which is an aluminosilicate glass
• Al O also contributes to the formation of a glass network and functions to improve glass stability and chemical durability.
• the total content of SiO and Al 0 is preferably 70% or more in order to improve the chemical durability, particularly the acid resistance, while improving the glass stability. In order to further improve the acid resistance, it is more preferable to set the total content to 75% or more, more preferably 76% or more. Considering the meltability of glass, the total content of SiO and Al 0 is 8
• 5% or less is preferable. 80% or less is more preferable.
• the SiO content is preferably 50% or more, more preferably 60% or more, still more preferably 62% or more, and even more preferably 65% or more.
• the SiO content is preferably 75% or less, more preferably 72% or less, and even more preferably 70% or less. preferable. If a substrate is made by processing glass containing undissolved material, part of the undissolved material may be exposed on the substrate surface, forming protrusions. A substrate having such protrusions cannot be used as a substrate for an information recording medium that requires high smoothness. Therefore, the meltability in the glass used for the information recording medium substrate is an important characteristic.
• a preferred range for the content of A10 is more than 0%, a more preferred range is 3% or more, a further preferred range is 5% or more, and a still more preferred range is 7% or more.
• the content of A1 0 be 15% or less 1
• a preferable range of the mol ratio is 0.040 or more. If the mo 1 ratio is excessive, the meltability tends to decrease or the glass stability tends to decrease, so the mo is preferably 0.18 or less and more preferably 0.15 or less. More preferably, it is more preferably 0.12 or less.
• MgO functions to improve the meltability, rigidity and hardness and to increase the thermal expansion coefficient.
• coexistence with CaO also has the effect of enhancing the stability as a glass.
• the content is preferably 0% or more and less than 5%.
• the MgO content is preferably less than 3%, more preferably 2% or less.
• a preferred lower limit for the MgO content is 0.1%, a more preferred lower limit is 0.3%, and a still more preferred lower limit is 0.5%.
• CaO functions to improve the devitrification resistance by improving the meltability, rigidity and hardness, increasing the thermal expansion coefficient, and introducing an appropriate amount.
• the content is preferably 0 to 5%.
• a more preferable lower limit of the CaO content is 0.1%, a further preferable lower limit is 0.5%, a more preferable upper limit is 4%, and a further preferable upper limit is 3%.
• SrO and BaO also have the function of improving the meltability and increasing the thermal expansion coefficient.
• the addition of SrO and BaO tends to lower the chemical durability, increase the specific gravity of the glass, and increase the raw material cost. Therefore, the total content of SrO and BaO is preferably 0 to 5%, more preferably 0 to 2%, and still more preferably 0 to 1%.
• a preferable range of the SrO content is 0 to 2%, and a more preferable range is 0 to 1%, and it is more preferable not to introduce SrO.
• a preferable range of the content of BaO is 0 to 2%, and a more preferable range is 0 to 1%, and it is more preferable not to introduce BaO.
• a clarifying agent such as Sb 0, SnO, or CeO may be added to glass IV as necessary.
• Sb 0 is not preferable.
• a glass for use in an information recording medium substrate is A glass for use in an information recording medium substrate.
• Glass V offers both excellent acid resistance and alkali resistance at the same time, so the substrate is constructed from glass V, and organic substances that are dirt on the glass surface are removed by acid treatment, and then adhesion of foreign substances is prevented by alkali treatment. The ability to obtain an extremely clean substrate while maintaining excellent smoothness can be achieved.
• the glass V has an etching rate of 3.0 nm / min or less, more preferably 2.5 nm / min when immersed in a 0.5% (Vol%) aqueous solution of Kay hydrofluoric acid (H SiF) kept at 50 ° C.
• the acid resistance is more preferably 2.0 nm / min or less, particularly preferably 1.8 nm / min or less.
• the glass V has an etching rate of O. lnm / min or less, more preferably 0.09 nm / min or less, and further preferably 0.08 when immersed in a 1% by mass potassium hydroxide aqueous solution kept at 50 ° C. It has alkali resistance of nm / min or less.
• the etching rate is defined by the depth of the glass surface cut per unit time.
• this is the depth of the glass substrate cut per unit time.
• the method for measuring the etching rate is not particularly limited, and examples thereof include the following methods. First, after processing the glass V into a substrate shape (flat plate shape), a mask treatment is applied to a part of the glass substrate in order to make an unetched portion, and the glass substrate in this state is treated with the aqueous solution of hydrofluoric acid or hydroxide. Immerse in a strong aqueous solution of lithium.
• the glass substrate is lifted from each of the above aqueous solutions and applied to the masked portion to obtain the difference (etching difference) between the portion and the portion. Thereby, the etching amount (etching rate) per unit time is obtained.
• the etching difference difference between the portion and the portion.
• the etching amount (etching rate) per unit time is obtained.
• the content of each component the total content is Displayed in mol%, and the ratio between contents is expressed in mo.
• Glass V is an oxide glass, and the content of each component is shown as a value converted to an oxide.
• a preferred embodiment of the glass V is aluminosilicate glass, which is a glass having a SiO content of 50% or more and a total content of SiO and A10 of 70% or more.
• SiO is an aluminosilicate glass network-forming component that improves glass stability, chemical durability, especially acid resistance, reduces thermal diffusion of the substrate, and increases the heating efficiency of the substrate by radiation. It is an essential ingredient.
• A10 also contributes to the formation of a glass network and works to improve glass stability and chemical durability.
• the total content of SiO and A10 is 70% or more in order to improve the chemical durability, particularly the acid resistance, while improving the glass stability. In order to further improve the acid resistance, the total content is preferably 75% or more, more preferably 76% or more. In consideration of the meltability of the glass, the total content of SiO and A10 is preferably 85% or less, more preferably 80% or less.
• the content of SiO is preferably 50% or more, more preferably 55% or more, still more preferably 60% or more, and more preferably, in order to improve glass stability and further improve acid resistance. Or 63% or more, more preferably 65% or more.
• the SiO content is preferably 75% or less, more preferably 72% or less, and more preferably 70% or less. Further preferred.
• Glass V is selected from the group force consisting of Li 0, Na 0 and K 0 as the glass component.
• One or more alkali metal oxides selected from the group consisting of MgO, CaO, SrO and BaO, and ZrO, HfO, Nb0, Ta0, LaO
• the total content of the alkali metal oxide and the alkaline earth metal oxide is 8 mol% or more
• alkali metal oxides selected from the group consisting of LiO, NaO and KO to maintain the meltability.
• alkaline earth metal oxides selected from the group consisting of MgO, CaO, SrO and BaO.
• Both alkali metal oxides and alkaline earth metal oxides are components useful for increasing the coefficient of thermal expansion to make them suitable for an information recording medium substrate, particularly a magnetic recording medium substrate.
• Zr ⁇ , Hf ⁇ , Nb0, Ta ⁇ , La0, Y0 and One or more oxides selected from the group consisting of TiO are introduced. If ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO are introduced excessively, the meltability and glass stability will decrease.
• the introduction amount is preferably determined by the balance between the alkali metal oxide and the alkaline earth metal oxide. Specifically, the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO relative to the total content of Li 0, Na 0, K 0, MgO, CaO, SrO and BaO mol ratio ((ZrO + HfO + Nb 0 + Ta 0 + La O + Y 0 + TiO) / (Li O + Na O + K 0
• the amount is 0.18 or less, more preferably 0.15 or less. It is more preferable to set it to 0.13 or less, and it is more preferable to set it to 0.12 or less.
• the total content of ZrO, HfO, NbO, TaO, LaO, YO and TiO 0.3% or more. It is more preferable to make it 0.5% or more 0.7. More preferably, it is at least 0 .
• the total content is preferably 4% or less, more preferably 3% or less, and more preferably 2% or less. More than 1.5% It is more preferable to set it down.
• Glass V A preferred embodiment contains at least one of LiO and NaO, and Li 0 and Na
• Li 0 and Na 0 are components that further improve the meltability, and are also necessary when chemically strengthening glass V. Furthermore, it has a strong function of imparting suitable thermal expansion characteristics to an information recording medium substrate, particularly a magnetic recording medium substrate, by increasing the thermal expansion coefficient.
• Li 0 and Na 0 as glass components, in order to obtain an effect of reducing or preventing the dissolution of alkali metal components by the mixed alkali effect.
• MgO functions to improve the meltability, rigidity, and hardness and to increase the thermal expansion coefficient.
• the content is preferably 0% or more and less than 5%.
• the MgO content is less than 3%, a more preferred upper limit is 2%, a preferred lower limit is 0.1%, a more preferred lower limit is 0.3%, and a further preferred lower limit is 0.5%.
• CaO functions to improve the devitrification resistance by improving the meltability, rigidity, and hardness, increasing the thermal expansion coefficient, and introducing an appropriate amount.
• the content is preferably 0 to 5%.
• a more preferable lower limit of the CaO content is 0.1%, a further preferable lower limit is 0.5%, a more preferable upper limit is 4%, and a further preferable upper limit is 3%.
• SrO and BaO also have the function of improving the meltability and increasing the thermal expansion coefficient.
• the addition of SrO and BaO tends to lower the chemical durability, increase the specific gravity of the glass, and increase the raw material cost. Therefore, the total content of SrO and BaO is preferably 0 to 5%, more preferably 0 to 2%, and still more preferably 0 to 1%.
• a preferable range of the SrO content is 0 to 2%, and a more preferable range is 0 to 1%, and it is more preferable not to introduce SrO.
• a preferable range of the content of BaO is 0 to 2%, and a more preferable range is 0 to 1%, and it is more preferable not to introduce BaO.
• Glass V may contain a clarifying agent such as Sb 0, SnO, or CeO if necessary.
• A10 is 5-20%, but the total amount of SiO and A10 is 74% or more,
• Li ⁇ exceeds 1% and below 9%, Na O 5-18%, provided that the mass ratio Li O / Na O is 0.5 or less,
• CaO exceeds 0% and 5% or less. However, the total amount of MgO and CaO is 5% or less, and the content of CaO is larger than the content of MgO.
• Glass VII is expressed in mass%.
• A10 is 5-20%, but the total amount of SiO and A10 is 74% or more,
• ZrO exceeds 0% and 5.5% or less
• Li ⁇ exceeds 1% and below 9%
• CaO exceeds 0% and 5% or less. However, the total amount of MgO and CaO is 5% or less, and the content of CaO is larger than the content of MgO.
• a substrate for an information recording medium having excellent surface smoothness even after cleaning with high chemical durability can be produced.
• Glass VI stipulates the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO, while glass VII stipulates the contents of ZrO and TiO separately. Since the points are common, the composition of Glass VI and VII will be explained in detail below. Glass VI and VII are both oxide glasses, and the content of each component is shown in terms of oxides. Unless otherwise specified, in Glasses VI and VII, the glass component content and the total content are expressed in mass%, and the content ratio is expressed in mass ratio. Shall be displayed.
• SiO is a glass network-forming component, and it is essential to improve glass stability, chemical durability, especially acid resistance, reduce substrate thermal diffusion, and increase substrate heating efficiency by radiation. It is an ingredient. If the content is less than 57%, it is difficult to obtain the above effect, and it is difficult to achieve the above purpose. On the other hand, if it exceeds 75%, the meltability is lowered and unmelted matter is produced in the glass. Therefore, the SiO content is 57 to 75%, preferably 63 to 70%, more preferably 63 to 68%.
• A10 also contributes to the formation of a glass network, and functions to improve glass stability and chemical durability. If the content power is less than 5%, it is difficult to obtain the above effect, and if it exceeds 20%, the meltability is lowered and unmelted material is produced in the glass. Therefore, the content of A10 is 5 to 20%, preferably 7 to 20%, more preferably 11 to 20%, still more preferably 12 to 20%, still more preferably 13 to 20%, still more preferably 13 ⁇ 18%, still more preferably 13-16%.
• SiO and A10 are mutually replaceable forces S.
• the total content of SiO and A10 is set to 74% or more.
• a preferred range of the total amount is 76% or more, a more preferred range is 78% or more, a still more preferred range is more than 79%, and even more preferred is 80% or more.
• glass VI ZrO, HfO, Nb0, Ta0, La0, Y0 and TiO are components that improve chemical durability, particularly alkali resistance, and increase rigidity and toughness. for that reason,
• the total content of ZrO, HfO, Nb 0, Ta 0, La 0, Y 0 and TiO is set to more than 0%. However, if the total content exceeds 6%, the glass stability is lowered, the meltability is lowered, and the specific gravity is increased. Therefore, ZrO, HfO, Nb 0, Ta 0, La 0, Y
• the total content of 0 and TiO should be more than 0% and not more than 6%.
• a preferable range of the total content is 5.5% or less, a more preferable range is 4% or less, and a further preferable range is 3% or less.
• the preferred lower limit of the content is 0.1%, the more preferred lower limit is 0.2%, the still more preferred lower limit is 0.5%, the more preferred lower limit is 1%, and the still more preferred lower limit is 1.4%.
• TiO when glass containing TiO is immersed in water, the reaction product of the glass and water may adhere to the glass surface. For this reason, other components are more advantageous in terms of water resistance. Therefore, from the top to maintain water resistance, Ti
• the content of O is preferably 0 to 1%, more preferably 0 to 0.5%, and even more preferably TiO is not introduced.
• HfO, Nb 0, Ta 0, and La 0 increase the specific gravity of the glass and increase the weight of the substrate. Therefore, the total content of HfO, Nb 0, Ta 0, and La O increases the weight of the substrate. 0 ⁇
• a range of 3% is preferable.
• a range of 0 to 2% is more preferable.
• a range of 0 to 1% is more preferable.
• the preferable content of each of 0 is 0 to 3%, the more preferable content is 0 to 2%, still more preferably 0 to 1%, and particularly preferably not introduced.
• Y 0 has a content of 0.
• a range of ⁇ 2% is preferred.
• a range of 0-1% is more preferred. More preferably, Yo is not introduced.
• ZrO has a function of improving chemical durability, particularly alkali resistance, and increases rigidity and toughness, and also has a function of increasing the efficiency of chemical strengthening.
• the mass ratio of ZrO content to the total content of ZrO, HfO, NbO, TaO, LaO, YO and TiO is in the range of 0.8 to 1. It is more preferable to be in the range of 0.9 to 1, more preferably 0.95 to 1, and even more preferably 1.
• ZrO is an essential component having the function of improving chemical durability, particularly alkali resistance, enhancing rigidity and toughness, and enhancing the efficiency of chemical strengthening by introducing even a small amount.
• the ZrO content is more than 0% and not more than 5.5%.
• a preferred range for the ZrO content is 0.1-5.5%.
• the preferable lower limit of the ZrO content is 0.2%, the more preferable lower limit is 0.5%, the more preferable lower limit is 1%, the more preferable lower limit is 1.4%, the preferable upper limit is 5%, the more preferable upper limit is 4%, and further A preferred upper limit is 3%.
• Alkali metal oxides such as LiO, NaO, and KO increase the meltability of glass.
• the thermal expansion coefficient is increased to give a suitable thermal expansion characteristic to an information recording medium substrate, particularly a magnetic recording medium substrate.
• glasses VI and VII the above alkali metal oxides Of these, Li 2 O and Na 2 O are essential components, and K ⁇ is an optional component.
• Li 2 O is a component that contributes to ion exchange during chemical strengthening and is introduced in an amount of more than 1%. However, since chemical durability decreases due to excessive introduction, the content exceeds 1% and is not more than 9%.
• the preferred lower limit for the Li 0 content is 1.5%, the more preferred lower limit is 2%, the preferred upper limit is 7%, the more preferred upper limit is 5%, the still more preferred upper limit is 4.5%, and the more preferred upper limit is 4.0%.
• Na 0 is a component that contributes to ion exchange during chemical strengthening, and is introduced in an amount of 5% or more. However, if it is introduced in excess of 18%, the chemical durability decreases, so the content is made 5-18%.
• the preferred lower limit of NaO content is 6%, the more preferred lower limit is 7%, the still more preferred lower limit is 8%, the still more preferred lower limit is 9%, the preferred upper limit is 17%, the more preferred upper limit is 16%, and still more preferred The upper limit is 15%.
• the ratio of Li 0 amount to Na 0 amount is 0.5 or less, preferably 0.45 or less
• the glass components that directly contribute to ion exchange during chemical strengthening are Li 0 and Na 0.
• alkali ions that contribute to ion exchange are Na ions and / or K ions.
• the amount of Li ion concentration in the molten salt increases by more than 0.5. The rise becomes remarkable, and the balance between alkali ions that contribute to ion exchange and alkali ions that do not contribute to ion exchange changes greatly from the start of treatment.
• Li O / Na 2 O is set within the above range. From the viewpoint of reducing or preventing elution of alkali metal components by the mixed alkali effect, Li
• K 0 is introduced in excess of 6%, which has the function as an alkali metal oxide, the chemical durability is lowered. Therefore, its content is 0 to 6%, preferably 0 to 3%. More preferably 0 to 2%, still more preferably 0 to 1%, and still more preferably 0.1 to 0.9%. A small amount of K 0 is introduced. Then, when chemically strengthening a large number of substrates, there is an effect of reducing variations in the compressive stress layer between the substrates.
• MgO functions to improve the meltability, rigidity, and hardness and to increase the thermal expansion coefficient.
• coexistence with CaO also has the effect of enhancing the stability as a glass.
• the ion exchange speed can be controlled so that the flatness does not deteriorate.
• the chemical durability decreases, so the content is made 0 to 4%.
• a preferable lower limit of the MgO content is 0.1%, a more preferable lower limit is 0.2%, and a preferable upper limit is 3.5%.
• CaO works to improve the devitrification resistance by improving the meltability, rigidity and hardness, increasing the thermal expansion coefficient, and introducing an appropriate amount. Furthermore, like MgO, it also functions to control the ion exchange speed during chemical strengthening. However, if it is introduced in excess of 5%, the chemical durability decreases, so the content exceeds 0% and is 5% or less.
• the preferred lower limit of CaO content is 0.1%, the more preferred lower limit is 0.3%, the still more preferred lower limit is 0.5%, the still more preferred lower limit is 1%, the preferred upper limit is 4%, and the more preferred upper limit is 3.5%.
• the chemical durability decreases when the total amount of MgO and CaO exceeds 5%, the total amount of MgO and CaO is 5% or less, preferably 4.5% or less, more preferably 4% or less.
• the CaO content is made larger than the MgO content.
• SrO and BaO also have the function of improving the meltability and increasing the thermal expansion coefficient, but lowering the chemical durability, increasing the specific gravity of the glass, and increasing the raw material cost.
• the total content of BaO is 0 to 3%, preferably 0 to 2%, more preferably 0 to 1%. It is even more preferable not to introduce Sr ⁇ . It's even better to use BaO.
• TiO decreases the water resistance due to the introduction of excessive force that acts to increase rigidity, so its content is 0 to 1%, preferably 0 to 0.5%, and more preferably not introduced.
• the TiO content of glass VI is as described above.
• ZnO also works in the same way as alkaline earth metal oxides, such as improving its meltability, but its devitrification resistance is reduced by excessive introduction.
• its content is, for example, less than 1%, preferably 0 to 0.9%, more preferably 0 to 0.5%. More preferably not.
• B 0 functions to improve meltability, but is volatile and may corrode refractories during glass melting, so its content is, for example, less than 2%, preferably 0 to 1.5%. More preferably, it is 0 to 1%, more preferably 0 to 0.4%, and it is more preferable not to introduce.
• the glass VI Gd, Yb, Er, Nd, Dy, Ho, Tm, Tb, Pm, and Pr can be introduced in order to increase rigidity and improve chemical durability.
• the total content is, for example, less than 2%, preferably 0-1.8%, more preferably 0-1.5%. More preferably, it is 0 to 1%, and more preferably 0 to 0.8%. Even more preferably, don't introduce.
• Ln 0 is a lanthanoid metal oxide, and its content in the glass VII is the total amount of the lanthanoid metal oxide contained in the glass.
• Ln 0 works to increase rigidity and chemical durability, so it can be introduced to increase rigidity and chemical durability.
• Examples of Ln include La, Gd, Y, Yb, Er, Nd, Dy, Ho, Tm, Tb, Pm, and Pr.
• the content thereof is, for example, less than 2%, preferably 0 to 1.8%, more preferably 0 to 1.5%, and further Preferably it is 0 to 1%, more preferably 0 to 0.8%. Even more preferably not introduced
• Sb 0, As 0, SnO, and CeO may be introduced as fining agents.
• As 0 imposes a burden on the environment, it is desirable not to use it especially when manufacturing substrates through the float process.
• Sb 0 should be avoided when the substrate is manufactured via the float process.
• a glass molded product that becomes the base material of the substrate is manufactured by press molding or cast molding. When manufactured, it can be used as an effective fining agent. The amount added is, for example,
• SnO and CeO can also be used when a substrate is manufactured through a float process.
• the addition amount is, for example, 0 to 1.0%, preferably 0 to 0.7%.
• the components in glass VII can be broadly divided into SiO, A10, ZrO, and alkali metal oxides.
• the ratio of A10 content to ZrO content should be 160 or less. It is more preferable to set it to 100 or less, more preferable to set it to 50 or less, and even more preferable to set it to 20 or less.
• the thermal diffusion of the glass can be reduced by setting the SiO content to a predetermined value or more.
• a film including an information recording layer is formed on the substrate by sputtering in a vacuum chamber. Therefore, it is preferable to heat the substrate by radiation. If the substrate is made of glass having a small thermal diffusion, the infrared rays are absorbed and the heat is hardly diffused from the heated substrate, so that the heating efficiency can be increased.
• glass I to VII it is also effective to increase the infrared absorption of the glass by introducing an additive that absorbs the infrared light just by reducing the thermal diffusion of the substrate.
• Such infrared absorption additives include Fe, Cu, Co, Yb, Mn, Nd, Pr, V, Cr, Ni, Mo, Ho, Er, water Minutes can be illustrated.
• Fe, Cu, Co, Yb, Mn, Nd, Pr, V, Cr, Ni, Mo, Ho, Er are forces that exist as ions in the glass. When these ions are reduced, they are deposited in the glass or on the surface of the substrate.
• the total content should be limited to 0 to 1%, preferably 0 to 0.5%, more preferably 0 to 0.2%. ,.
• the amount of Fe introduced in terms of Fe 0 is preferably 1% or less, more preferably 0.5% or less, more preferably 0.2% or less, and further preferably 0.1% or less. It is even more preferable to make it 0.05% or less.
• a preferred lower limit is 0.01%, and a more preferred lower limit is 0.03%.
• a particularly preferred range is 0.03 to 0.02%.
• glass raw materials containing these additives as impurities for example, silica raw materials may be used.
• the amount of impurities is required to be constant, the above points should be noted when selecting raw materials.
• Fe is alloyed with platinum or platinum alloy that constitutes a glass melting vessel, a stirring rod, and a tube for flowing glass, and damages the vessel, stirring rod, and tube. In this case, it is preferable to suppress the addition amount of Fe. In such a case, it is more preferable not to introduce Fe 0.
• PbO is not recommended because it increases the specific gravity of the glass, which has a large environmental impact.
• the glasses VI and VII basically have SiO, A1 0, ZrO, Li 0, Na as glass components.
• the total content of K, MgO, and CaO is 99% or more.
• glass raw materials such as oxides, carbonates, nitrates, sulfates and hydroxides are weighed and mixed to prepare blended raw materials.
• This raw material is heated in a refractory furnace and melted at a temperature of, for example, 1400 to: 1600 ° C, and clarified and homogenized. In this way, a homogeneous molten glass free of bubbles and unmelted material
• the glass can be obtained by making, flowing out, and forming into a predetermined shape.
• the present invention relates to a chemically strengthened glass for use in an information recording medium substrate obtained by subjecting the information recording medium substrate glass of the present invention to a chemical strengthening treatment.
• the chemically strengthened glass has the characteristics of the glass for information recording medium substrate of the present invention described above. Moreover, as described above, according to the glass for an information recording medium substrate of the present invention, it is possible to avoid the problem that the shape is varied depending on the substrate due to the chemical strengthening treatment and the inner diameter dimensional tolerance of the center hole of the substrate is increased. be able to. Therefore, the chemically strengthened glass obtained by chemically strengthening the glass for an information recording medium substrate of the present invention is suitable as a substrate for an information recording medium having a high recording density with a small inner diameter dimensional tolerance of the center hole. .
• the chemical strengthening of the glasses I to VII is performed, for example, by immersing the glass processed into a disk shape in an alkali molten salt.
• an alkali molten salt sodium nitrate molten salt, potassium nitrate molten salt, or a mixture of the above two molten salts can be used.
• the chemical strengthening treatment means that a part of ions contained in the glass substrate are contained in the chemical strengthening treatment liquid by bringing the glass substrate into contact with the chemical strengthening treatment liquid (molten salt).
• the glass substrate is chemically strengthened by substituting ions larger than ions.
• the molten salt temperature at the time of chemical strengthening is preferably higher than the strain point of the glass and lower than the glass transition temperature, and within a temperature range in which the molten salt does not thermally decompose.
• the concentration of each alkali ion in the molten salt gradually changes, and glass components other than Li and Na are dissolved in a trace amount. As a result, the processing conditions deviate from the optimum range as described above.
• Such variations in chemical strengthening due to changes in molten salt over time can be reduced by adjusting the composition of the glass constituting the substrate as described above, but on that basis, the concentration of K ions in the molten salt should be set high. Therefore, the variation can be reduced.
• the chemical strengthening treatment is applied to the glass. Confirm by observing and confirming the surface (surface that cuts the treatment layer) by the Babinet method, or measuring the depth direction distribution of Al force reions (eg, U + , Na + , K + ) from the glass surface. That power S.
• the present invention relates to a glass substrate for an information recording medium constituted by any one of the glasses I to VII.
• the glass substrate for information recording media of the present invention is composed of glass I to VII having excellent chemical durability as described above, it maintains high surface smoothness even after cleaning for removing foreign substances. can do. Furthermore, since the glass substrate for information recording media of the present invention has little variation in shape due to the substrate even after chemical strengthening treatment, it is possible to reduce the tolerance of the inner diameter of the center hole, and information recording with a high recording density is possible. It is suitable as a medium substrate. According to the present invention, for example, an information recording medium that satisfies the current inner diameter dimension tolerance standard (within ⁇ 0.025 mm) can be obtained, and further, an information recording that can cope with stricter specifications such as an inner diameter dimension tolerance within ⁇ 0.010 mm. It is also possible to obtain a medium.
• the current inner diameter dimension tolerance standard within ⁇ 0.025 mm
• a glass having a low elution of alkali metal components can provide a substrate having excellent impact resistance with less alkali elution due to chemical strengthening.
• bending strength is used as an index of impact resistance of an information recording medium substrate.
• a glass substrate for an information recording medium substrate of the present invention a glass substrate for an information recording medium having a bending strength of, for example, 10 kg or more, preferably 15 kg or more, and further 20 kg or more can be obtained.
• the bending strength can be obtained as a load value when a steel ball is placed in the center hole of the substrate placed on the holder and a load is applied by the load cell, causing the substrate to break.
• the measurement can be performed using, for example, a bending strength measurement tester (Shimadzu Autograph DDS-200).
• Information recording media include magnetic recording media, magneto-optical recording media, optical recording media, and the like, depending on the recording / reproducing method.
• the substrate of the present invention is particularly suitable as a magnetic recording medium substrate that requires high flatness and smoothness.
• Magnetic recording media are called magnetic disks, hard disks, etc., and record and reproduce internal storage devices (fixed disks, etc.), images and Z or audio, such as desktop computers, server computers, notebook computers, and mopile computers.
• the substrate of the present invention has, for example, a thickness of 1.5 mm or less, preferably 1.2 mm or less, more preferably 1 mm or less, and a lower limit of preferably 0.3 mm.
• the glass of the present invention particularly glass VI and VII, is adjusted to a range where swell due to chemical strengthening is unlikely to occur due to the balance of each component. Therefore, a thin substrate with excellent flatness can be obtained even after chemical strengthening treatment.
• the substrate of the present invention has a disk shape (disk shape) and can have an opening (center hole) at the center. According to the glass of the present invention, variation in shape due to the substrate after the chemical strengthening treatment can be reduced, so that a disk-shaped substrate having a small inner diameter dimensional tolerance of the center hole can be mass-produced.
• the present invention relates to a method for producing a glass substrate for an information recording medium, comprising a step of mirror polishing the glass for an information recording medium substrate of the present invention and a cleaning step of performing acid cleaning and alkali cleaning after mirror polishing.
• the said manufacturing method is suitable as a manufacturing method of the board
• molten glass is inserted into a heat-resistant mold to form a cylindrical glass, and after annealing, the side surface is ground by centerless processing, etc., and then sliced to a predetermined thickness to form a thin disk-shaped substrate Make a blank.
• the molten glass is flowed out into a float bath, formed into a sheet shape, annealed, and then cut through a disk-shaped substrate blank to produce a substrate blank.
• the substrate blank thus produced is provided with a center hole, or is subjected to inner and outer peripheral processing, lapping, polishing, and finished into a disk-shaped substrate. Thereafter, the substrate is washed with a detergent such as acid or alkali, rinsed, dried, and then subjected to the above-described chemical strengthening as necessary. Further, the chemical strengthening treatment can be performed after the mirror polishing process and before the cleaning process.
• a detergent such as acid or alkali
• the substrate is exposed to acid, alkali, and water in a series of steps, but the glass for information recording medium substrate of the present invention has excellent acid resistance, alkali resistance, and water resistance.
• a substrate having a flat and smooth surface that does not become rough can be obtained.
• a substrate with improved adhesion and less adhesion can be obtained.
• the glass substrate for information recording media (glass substrate for magnetic disk) is subjected to lapping and polishing so that the substrate surface (main surface) is a surface for recording information.
• the surface shape is formed.
• deposits of polishing abrasive grains are present on the main surface immediately after finishing polishing (mirror polishing).
• mirror polishing deposits of polishing abrasive grains are present on the main surface immediately after finishing polishing (mirror polishing).
• mirror polishing deposits of polishing abrasive grains are present on the main surface immediately after finishing polishing (mirror polishing).
• a chemical strengthening process is performed after a mirror polishing process
• the surface shape of the main surface is changed by the chemical strengthening process, and the reinforcing salt adheres to the main surface. Therefore, it is necessary to perform cleaning.
• This cleaning includes acid cleaning and / or alkali cleaning, and both are often performed.
• the glass substrate for the information recording medium has poor acid resistance and alkali resistance
• the surface of the substrate is roughened by cleaning.
• the cleaning agent is weakened to prevent the surface of the substrate from being roughened by cleaning, the abrasive grains adhering to the substrate surface, reinforcing salts, etc. cannot be removed sufficiently. Therefore, in order to reduce deposits containing abrasive grains and improve the smoothness of the substrate surface, the glass substrate for information recording media is required to have sufficient acid resistance and alkali resistance.
• an information recording medium having a high recording density of, for example, a recording density of 130 Gbit / inch 2 or more, more preferably 200 Gbit / inch 2 or more is required.
• a recording density of 130 Gbit / inch 2 or more it is effective to reduce the flying height of the recording / reproducing head with respect to the information recording medium.
• the surface roughness (Ra) of the main surface of the glass substrate for information recording medium is 0.25 nm or less.
• the “main surface” refers to the surface on which the information recording layer is provided or This is the surface that is provided. This surface is called the main surface because it is the surface with the largest area of the surface of the information recording medium.
• the circular surface of the disk (when there is a central hole) Corresponds to (except the center hole).
• the abrasive grains used in the mirror polishing process are not particularly limited as long as the main surface of the glass substrate for information recording medium can achieve, for example, a roughness Ra of 0.25 nm or less.
• silicon dioxide is more preferred. It is more preferable to create the surface shape of the glass substrate by performing acidic polishing or alkaline polishing using the colloidal silica in the form of silicon dioxide S colloid.
• acidic cleaning is preferable in that it mainly removes organic substances adhering to the substrate surface.
• alkali cleaning is preferable in terms of removing inorganic substances (for example, iron) adhering to the substrate surface.
• inorganic substances for example, iron
• the acid resistance and alkali resistance required for the glass substrate for information recording medium will be described below.
• the glass substrate has an etching rate of 3.0 nm / min or less, more preferably 2.5 nm / min or less when immersed in a 0.5% (Vol%) aqueous solution of kaleic acid (H SiF) kept at 50 ° C. More preferably, the acid resistance is 2.0 nm / min or less, particularly preferably 1.8 nm / min or less, and the etching rate when immersed in a 1 mass% potassium hydroxide aqueous solution maintained at 50 ° C. is 0.1. It is preferable to have alkali resistance which is not more than 0.09 nm / minute, more preferably not more than 0.08 nm / minute, more preferably 0.08 nm / minute or less.
• the glass substrate has high acid resistance and alkali resistance, a glass substrate having a smooth surface and a reduced amount of deposits attached to the substrate surface can be produced.
• glass which comprises this glass substrate glass V is mentioned, for example.
• the present invention relates to an information recording medium having an information recording layer on the glass substrate for information recording medium. Furthermore, this invention relates to the manufacturing method of the information recording medium which manufactures the glass substrate for information recording media by the manufacturing method of the glass substrate for information recording media of this invention, and forms an information recording layer on the said glass substrate.
• a substrate having high surface smoothness and excellent shape stability after chemical strengthening treatment can be produced.
• the information recording medium having the substrate is suitable for high density recording.
• a substrate with high heating efficiency can be obtained as described above, an information recording medium can be manufactured with high productivity.
• the information recording medium can be used as various information recording media by appropriately selecting an information recording layer.
• Examples of such a medium include a magnetic recording medium, a magneto-optical recording medium, and an optical recording medium.
• the information recording medium of the present invention can cope with an increase in recording density and can be suitably used as a perpendicular magnetic recording type magnetic recording medium.
• the information recording medium of the perpendicular magnetic recording system it is possible to provide an information recording medium that can cope with higher recording density. That is, the perpendicular magnetic recording type magnetic recording medium has a higher recording density (for example, 100 GBit / (2.5 cm) 2 or higher) than the conventional long magnetic recording type magnetic recording medium (for example, lTBit / (2.5cm) 2 ), so it is possible to achieve higher density recording power.
• the information recording medium of the present invention has an information recording layer on the aforementioned information recording medium substrate.
• an information recording medium such as a magnetic disk can be manufactured by sequentially providing an underlayer, a magnetic layer, a protective layer, a lubricating layer, and the like on the glass substrate.
• the information recording layer can be appropriately selected depending on the type of the medium and is not particularly limited.
• a Co-Cr system here, the system means a material containing the indicated substance
• Co-Cr-Pt-based Co-Ni-Cr-based, Co-Ni-Pt-based, Co_Ni_Cr_Pt-based, and Co_Cr_Ta-based magnetic layers.
• a Ni layer, a Ni-P layer, a Cr layer, or the like can be adopted.
• a material for a magnetic layer (information recording layer) suitable for increasing the recording density a Co CrPt alloy material, particularly a CoCrPtB alloy material can be mentioned.
• FePt series Alloy materials are also suitable. These magnetic layers are particularly useful when used as magnetic materials for perpendicular magnetic recording. CoCrPt alloy materials are adjusted at 300 ° C to 500 ° C, and FePt alloy materials are heated at a high temperature of 500 ° C to 600 ° C. It is possible to adopt a configuration suitable for increasing the recording density.
• the underlayer a nonmagnetic underlayer and / or a soft magnetic underlayer can be used.
• the nonmagnetic underlayer is mainly provided for the purpose of reducing the crystal grains (crystal grains) of the magnetic layer or controlling the crystal orientation of the magnetic layer.
• a bcc crystalline underlayer for example, a Cr-based underlayer, has the effect of promoting in-plane orientation, so hep-based crystalline underlayers preferred for in-plane (longitudinal) recording magnetic disks,
• Ti-based underlayers and Ru-based underlayers have the effect of promoting vertical alignment, and can be used as magnetic disks for perpendicular magnetic recording systems.
• the amorphous underlayer has the function of refining the crystal grains of the magnetic layer.
• the soft magnetic underlayer is an underlayer mainly used for a perpendicular magnetic recording disk, and has a function of promoting magnetization pattern recording on the perpendicular magnetic recording layer (magnetic layer) of the magnetic head.
• a layer having a high saturation magnetic flux density and a high magnetic permeability is preferable. Therefore, it is preferable to perform high-temperature film formation or post-deposition heat treatment.
• soft magnetic layer materials include Fe-based soft magnetic materials such as FeTa-based soft magnetic materials and FeTaC-based soft magnetic materials. CoZr-based soft magnetic materials and CoTaZr-based soft magnetic materials are also preferred.
• a carbon film or the like can be used, and in order to form the lubricating layer, a perfluoropolyether-based lubricant can be used.
• Preferred embodiments of the perpendicular magnetic recording disk include a soft magnetic underlayer, an amorphous nonmagnetic underlayer, a crystalline nonmagnetic underlayer, a perpendicular magnetic recording layer (magnetic layer), and a protective layer on the substrate of the present invention.
• a magnetic disk having a lubricating layer formed in this order can be mentioned.
• the film structure formed in a substrate shape is a single layer film in which a perpendicular magnetic recording layer is formed on a glass substrate which is a nonmagnetic material, a soft magnetic layer and a magnetic layer.
• Preferred examples include a two-layer film in which recording layers are sequentially stacked, and a three-layer film in which hard magnetic layers, soft magnetic layers, and magnetic recording layers are sequentially stacked.
• the two-layer film and the three-layer film are simple. This is preferable because it is more suitable than the layer film for higher recording density and stable maintenance of the magnetic moment.
• the glass substrate for an information recording medium of the present invention it is possible to suitably manufacture a magnetic disk that is used for recording and reproduction at a surface information recording density of 200 gigabits per square inch or more. It is.
• a magnetic disk corresponding to a perpendicular magnetic recording system As a magnetic disk corresponding to a surface information recording density of 200 gigabits per square inch or more, a magnetic disk corresponding to a perpendicular magnetic recording system can be mentioned.
• the magnetic head When recording and reproducing information with a surface information recording density of 200 gigabits per square inch or more in a hard disk drive, the magnetic head that floats and faces the main surface of the magnetic disk and records and reproduces the signal.
• the flying height relative to the magnetic disk is 8 nm or less.
• the main surface of the magnetic disk is usually in a mirror state.
• the main surface of the magnetic disk usually needs to have a surface roughness Ra of 0.25 mm or less.
• the recording / reproducing element mounted on the magnetic head is called a Dynamic Flying Height type head (hereinafter DFH type head).
• DFH type head Dynamic Flying Height type head
• the element periphery of the magnetic head is thermally expanded by heating the surroundings of the element, and the gap between the magnetic head and the magnetic disk is further narrowed. Therefore, the main surface of the magnetic disk has a surface roughness Ra.
• the mirror surface must be less than 0.25 awakening. According to the glass substrate for an information recording medium of the present invention, a magnetic disk corresponding to a DFH type head can be preferably produced.
• the glass substrate for an information recording medium of the present invention may be amorphous glass. With amorphous glass, it is possible to create a mirror surface with a suitable surface roughness.
• FIG. 1 shows an example of the configuration of a magnetic disk 10 according to an embodiment of the present invention.
• the magnetic disk 10 has a glass substrate 12, an adhesion layer 14, a soft magnetic layer 16, an underlayer 18, a miniaturization promoting layer 20, a magnetic recording layer 22, a protective film 24, and a lubricating layer 26 in this order.
• the magnetic recording layer 22 functions as an information recording layer for recording and reproducing information.
• the magnetic disk 10 may further include an amorphous seed layer between the soft magnetic layer 16 and the underlayer 18.
• the seed layer is a layer for improving the crystal orientation of the underlayer 18.
• the underlayer 18 is Ru
• the seed layer is a layer for improving the C-axis orientation of the hep crystal structure.
• the glass substrate 12 is a glass substrate for forming each layer of the magnetic disk 10.
• the glass substrate for information recording media of the present invention described above is used as this glass substrate.
• the surface roughness of the main surface of the glass substrate is preferably a mirror surface with Ra of 0.25 nm or less.
• the surface roughness Rmax is preferably a mirror surface of 3 nm or less.
• the separation distance between the magnetic recording layer 22 which is a perpendicular magnetic recording layer and the soft magnetic layer 16 can be made constant. Therefore, a suitable magnetic circuit can be formed between the head magnetic recording layer 22 and the soft magnetic layer 16.
• the adhesion layer 14 is a layer for improving adhesion between the glass substrate 12 and the soft magnetic layer 16, and is formed between the glass substrate 12 and the soft magnetic layer 16. By using the adhesion layer 14, peeling of the soft magnetic layer 16 can be prevented.
• the material of the adhesion layer 14 for example, a Ti-containing material can be used. From a practical viewpoint, the thickness of the adhesion layer 14 is preferably 1 nm to 50 nm.
• the material of the adhesion layer 14 is preferably an amorphous material.
• the soft magnetic layer 16 is a layer for adjusting the magnetic circuit of the magnetic recording layer 22.
• 16 is not particularly limited as long as it is formed of a magnetic material exhibiting soft magnetic properties.For example, it may have a magnetic property of 0.01 to 80 Oersted, preferably 0.01 to 50 Oersted in terms of coercive force (He). I like it. Also, saturation magnetic flux density
• the material of the soft magnetic layer 16 includes Fe-based and Co-based materials.
• Fe-based soft magnetic materials such as FeTaC-based alloy, FeTaN-based alloy, FeNi-based alloy, FeCoB-based alloy and FeCo-based alloy, Co-based soft magnetic materials such as CoTaZr-based alloy and CoNbZr-based alloy, Alternatively, FeCo alloy soft magnetic material or the like can be used.
• an amorphous material is suitable.
• the thickness of the soft magnetic layer 16 is, for example, 30 nm to 1000 nm, more preferably 50 nm to 200 nm.
• the thickness exceeds 1000 mm, sputtering film formation may be difficult.
• the underlayer 18 is a layer for controlling the crystal directions of the miniaturization promoting layer 20 and the magnetic recording layer 22, and includes, for example, ruthenium (Ru).
• the foundation layer 18 is formed of a plurality of layers.
• the layer including the interface in contact with the miniaturization promoting layer 20 is formed of Ru crystal particles.
• the miniaturization promoting layer 20 is a nonmagnetic layer having a dull-fluctuating structure.
• the miniaturization promoting layer 20 is made of a nonmagnetic CoCrSiO material having a dull-fluctuating structure.
• the miniaturization promoting layer 20 has a single-layer structure composed of an oxide grain boundary portion containing SiO and a metal particle portion containing CoCr partitioned by the grain boundary portion.
• the magnetic recording layer 22 has a ferromagnetic layer 32, a magnetic coupling control layer 34, and an exchange energy control layer 36 on the miniaturization promoting layer 20 in this order.
• the ferromagnetic layer 32 is a CoCrPtSiO layer having a Dara-yura structure, and has CoCrPt crystal particles as magnetic crystal particles.
• the ferromagnetic layer 32 has a single-layer structure composed of an oxide grain boundary part containing SiO and a metal grain part containing CoCrPt partitioned by the grain boundary part.
• the magnetic coupling control layer 34 is a coupling control layer for controlling the magnetic coupling between the ferromagnetic layer 32 and the exchange energy control layer 36.
• the magnetic coupling control layer 34 is made of, for example, a palladium (Pd) layer or a platinum (Pt) layer. Further, the film thickness of the magnetic coupling control layer 34 is, for example, 2 nm or less, and more preferably 0.5 to 1.5 nm.
• the exchange energy control layer 36 is a magnetic layer (continuous layer) in which easy axes of magnetization are aligned in substantially the same direction as the ferromagnetic layer 32.
• the exchange energy control layer 36 improves the magnetic recording characteristics of the magnetic disk 10 by exchange coupling with the ferromagnetic layer 32.
• the exchange energy control layer 36 includes, for example, an alternating multilayer film of cobalt (Co) or an alloy thereof and palladium (Pd) ([CoX / P d] n), or a multilayer film composed of alternating layers of cobalt (Co) or an alloy thereof and platinum (Pt) ([CoX / Pt] n). preferable. More preferably, 3 to 6 nm is suitable.
• the protective film 24 is a protective layer for protecting the magnetic recording layer 22 by the impact force of the magnetic head.
• the lubrication layer 26 is a layer for improving the lubricity between the magnetic head and the magnetic disk 10.
• each layer of the magnetic disk 10 excluding the lubricating layer 26 and the protective film 24 it is preferable to form a film by a sputtering method.
• the DC magnetron sputtering method is preferable because uniform film formation is possible.
• the protective film 24 is preferably formed by a CVD method using hydrocarbon as a material gas.
• the lubricating layer 26 can be formed by a dip method.
• an amorphous layer for example, the adhesion layer 14
• the soft magnetic layer 16 is preferably made of an amorphous material. According to the present invention, it is possible to reflect the surface roughness of a glass substrate in a mirror state where, for example, Ra is 0.25 nm or less, and to obtain a mirror surface magnetic disk surface where, for example, Ra is 0.25 nm or less.
• the information recording medium substrate eg, magnetic disk substrate
• information recording medium eg, magnetic disk
• it can be downsized.
• it is suitable as a magnetic disk substrate or a magnetic disk having a nominal diameter of 2.5 inches and a smaller diameter (for example, 1 inch).
• Example 1 Example 1 ', Example 2, Example 2', Example 3, Example 3 'shown in Table 1
• Example 4 Oxides, carbonates, nitrates, hydroxides, etc. so as to obtain a glass with a composition of 15
• the raw materials were weighed and mixed to obtain a blended raw material. This raw material was put into a melting vessel, heated and melted in the range of 1400-1600 ° C for 6 hours, clarified and stirred to produce a homogeneous molten glass free of bubbles and unmelted products.
• the lower mold on which the molten glass block was placed was immediately taken out from below the pipe, and was pressed into a thin disk shape with a diameter of 66 mm and a thickness of 1.2 mm using the upper mold and barrel mold facing the lower mold. After the press-formed product was cooled to a temperature at which it was not deformed, it was removed from the mold and annealed to obtain a substrate blank.
• molten glass that flows out was formed one after another using a plurality of lower molds.
• a disk-shaped substrate blank was produced by the following method A or B.
• the molten glass was continuously poured into the heat-resistant vertical through-hole provided with a cylindrical through-hole from the top, formed into a columnar shape, and taken out from the lower side of the through-hole. After annealing the taken-out glass, the glass was sliced at regular intervals in a direction perpendicular to the cylinder axis using a multi-wire saw, and a disk-shaped substrate blank was produced.
• the molten glass was poured out on a float bath and formed into a sheet-like glass. Next, after annealing, a disc-shaped glass was cut out from the sheet glass to obtain a substrate blank.
• a through-hole is drilled in the center of the substrate blank obtained by each of the above methods, and the outer and inner circumferences are ground.
• the main surface of the disk is lapped and polished (mirror polishing) to have a diameter of 65 mm and a thickness of 0.7 Finished on a magnetic disk substrate of mm.
• the dried substrate was subjected to chemical strengthening by being immersed in a mixed molten salt of sodium nitrate and potassium nitrate heated to 380 ° C. for 240 minutes, and then washed and dried.
• the chemically strengthened substrate did not show any swell due to chemical strengthening and had high flatness.
• the inner diameter of the center hole of the disk-shaped glass substrate is within the range of 20.025 mm ⁇ 0.010 mm, and the tolerance was made smaller than the current inner diameter dimension tolerance standard (tolerance ⁇ 0.025 mm).
• an underlayer, a soft magnetic layer, a magnetic layer, a lubricating layer, and the like were formed on the substrate to produce a perpendicular magnetic recording type magnetic disk.
• the liquidus temperature is an index of glass stability and devitrification resistance
• the preferred liquidus temperature for the glass for information recording medium substrate is 1000 ° C or lower, more preferably 970 ° C or lower, and still more preferably 95.
• the range is 0 ° C or lower, more preferably 930 ° C or lower.
• the lower limit is not particularly limited, but if you consider 800 ° C or higher as a guideline.
• Example 4 the board
• a glass having the composition described in Example 3 was molded by a direct press method to obtain an amorphous disk-shaped glass substrate. Thereafter, a hole was made in the central portion of the obtained glass substrate using a grindstone to obtain a disk-shaped glass substrate having a circular hole in the center. In addition, chamfering force was applied to the outer peripheral end face and the inner peripheral end face.
• the surface roughness of the end surface (inner circumference, outer circumference) of the glass substrate by brush polishing is about 1.0 ⁇ at the maximum height (Rmax), and 0.3 at the arithmetic average roughness (Ra). Polishing was performed to about ⁇ m.
• the surface of the glass substrate was ground using a # 1000 grain size so that the flatness of the main surface was 3 ⁇ m, the Rmax force was 3 ⁇ 4 ⁇ m, and the Ra force was 3 ⁇ 4.2 ⁇ .
• the flatness is a distance (height difference) between the highest part and the lowest part of the substrate surface in the vertical direction (direction perpendicular to the surface), and was measured with a flatness measuring device.
• AFM atomic force microscope
• a preliminary polishing process was performed using a polishing apparatus that can polish both main surfaces of 100 to 200 glass substrates at a time.
• a hard polisher was used for the polishing pad.
• a polishing pad previously containing zirconium oxide and cerium oxide was used.
• the polishing liquid in the preliminary polishing step was prepared by mixing cerium oxide abrasive grains having an average particle diameter of 1.1 ⁇ with water. The abrasive grains having a grain diameter exceeding 4 ⁇ were removed in advance. When the polishing liquid was measured, the maximum value of the abrasive grains contained in the polishing liquid was 3.5 / m, the average value was l.lzm, and the D50 value was l.lxm.
• the load held on the glass substrate was 80 to 100 gm 2
• the removal thickness of the surface portion of the glass substrate was 20 to 40 ⁇ m.
• a mirror polishing process was performed using a planetary gear type polishing apparatus capable of polishing both main surfaces of 100 to 200 glass substrates at a time.
• a soft polisher was used for the polishing pad.
• the polishing liquid in the mirror polishing process was prepared by adding sulfuric acid and tartaric acid to ultrapure water and further colloidal silica particles having a grain diameter of 40 nm.
• the sulfuric acid concentration in the polishing liquid was set to 0.15% by mass, and the pH value of the polishing liquid was set to 2.0 or less.
• the concentration of tartaric acid was 0.8% by mass, and the content of colloidal silica particles was 10% by mass.
• the pH value of the polishing liquid could be kept substantially constant without fluctuation.
• the polishing liquid supplied to the surface of the glass substrate was collected using a drain, cleaned by removing foreign substances with a mesh filter, and then reused by supplying it again to the glass substrate.
• the polishing speed in the mirror polishing process was 0.25 ⁇ / min, and it was found that an advantageous polishing speed could be realized under the above conditions.
• the polishing speed was obtained by dividing the amount of reduction in glass substrate thickness (processing allowance) required for finishing to a predetermined mirror surface by the required polishing time.
• the glass substrate was immersed in an aqueous NaOH solution having a concentration of 3 to 5% by mass for alkali cleaning. Cleaning was performed by applying ultrasonic waves. Furthermore, it was washed by sequentially immersing it in each washing tank of neutral detergent, pure water, pure water, isopropyl alcohol, and isopropyl alcohol (steam drying). The surface of the glass substrate after cleaning was observed with AFM (Digital Instruments Neon Nanoscope) (measured in a rectangular area of 5 ⁇ m x 5 ⁇ m). Adhesion of abrasive grains was not confirmed. Also, no foreign matter such as stainless steel or iron was found. Moreover, the increase in the roughness of the substrate surface before and after the cleaning was not observed.
• AFM Digital Instruments Neon Nanoscope
• a cleaned glass substrate preheated to 300 ° C is immersed in a chemically strengthened salt mixed with potassium nitrate (60% by mass) and sodium nitrate (40% by mass) and heated to 375 ° C for about 3 hours.
• the chemical strengthening process was performed.
• lithium ions and sodium ions on the surface of the glass substrate are replaced with sodium ions and potassium ions in the chemically strengthened salt, respectively, and the glass substrate is chemically strengthened.
• the thickness of the compressive stress layer formed on the surface of the glass substrate was about 100 to 200 zm.
• the glass substrate after the rapid cooling was immersed in sulfuric acid heated to about 40 ° C. and washed while applying ultrasonic waves. Thereafter, the glass substrate was washed with a 0.5% (Vol%) aqueous solution of key hydrofluoric acid (H SiF), and then the glass substrate was washed with a 1% by mass aqueous potassium hydroxide solution.
• the glass substrate 12 for magnetic disks was manufactured by the above process.
• the surface roughness of the glass substrate for magnetic disks was measured with an AFM (Atomic Force Microscope) (measured in a rectangular area of 5 / m ⁇ 5 ⁇ m).
• the maximum peak height (Rmax) was 1.5 nm, and the arithmetic average
• the roughness (Ra) was 0.15 nm.
• the surface was in a clean mirror state, and there was no foreign matter that obstructed the flying of the magnetic head or foreign matter causing thermal asperity failure.
• the increase in the roughness of the substrate surface before and after cleaning was unseen.
• the bending strength was measured.
• the bending strength is measured when the glass substrate breaks when a load is applied to the glass substrate as shown in Fig. 2 using a bending strength measurement tester (Shimadzu Autograph DDS-2000). It calculated
• acid cleaning and alkali cleaning are performed after chemical strengthening, but acid cleaning and alkali cleaning may be performed in the cleaning after the mirror polishing step.
• FIG. 1 schematically shows the film configuration (cross section) on the substrate 12.
• the adhesion layer 14 and the soft magnetic layer 16 were sequentially formed in an Ar atmosphere by a DC magnetron sputtering method using a film forming apparatus that was evacuated.
• the adhesion layer 14 was formed using a CrTi target so as to be an amorphous CrTi layer of 20 nm.
• the soft magnetic layer 16 is 200 nm amorphous.
• the film was formed using a CoTaZr target so that the lower layer was 21: 0:88 atomic%, Ta: 7 atomic%, Zr: 5 atomic%).
• the magnetic disk 10 having been deposited up to the soft magnetic layer 16 was taken out of the deposition apparatus and the surface roughness was measured in the same manner. The result was a smooth mirror surface with Rmax of 2.1 nm and Ra of 0.20 nm. .
• the coercive force (He) was 2 Elsted and the saturation magnetic flux density was 810 emu c.
• the underlayer 18 has a two-layer structure having a first layer and a second layer.
• a 10 nm thick layer made of amorphous NiTa (Ni: 40 atomic%, Ta: 10 atomic%) is formed on the disk substrate as the first layer of the underlayer 18. Then, a Ru layer having a thickness of 10 to 15 nm was formed as the second layer.
• a miniaturization promoting layer 20 having a hep crystal structure of 2 to 20 nm was formed using a nonmagnetic CoCr-SiO target. Further, a ferromagnetic layer 32 having a hep crystal structure of 15 nm was formed using a hard magnetic target having CoCrPt-SiO force.
• the composition of the target for the creation of the ferromagnetic layer 32 is Co: 62 atom%, Cr: 10 atom%, Pt: 16 atom%, SiO: 12 atom
• a magnetic coupling control layer 34 composed of a Pd layer was formed, and an exchange energy control layer 36 composed of a [CoB / Pd] n layer was formed.
• a protective film 24 made of hydrogenated carbon was formed by a CVD method using ethylene as a material gas. Since the film hardness is improved by using hydrogenated carbon, the magnetic recording layer 22 can be protected against an impact from the magnetic head.
• a lubricating layer 26 made of PFPE (perfluoropolyether) was formed by a dip coating method.
• the film thickness of the lubricating layer 26 is lnm.
• the obtained magnetic disk 10 was mounted on a 2.5-inch load / unload hard disk drive.
• the magnetic head mounted on this hard disk drive is a Dynamic Flying Height (abbreviation: DFH) type magnetic head.
• the flying height of this magnetic head with respect to the magnetic disk is 8 nm.
• LUL load unload
• the LUL test is performed with a 2.5-inch hard disk drive rotating at 5400 mm and a magnetic head with a flying height of 8 nm.
• the magnetic head described above was used.
• the shield part is made of NiFe alloy.
• a magnetic disk is mounted on this magnetic disk device, and the LUL operation is continuously performed by the magnetic head described above, and the number of times the LUL is durability is measured.
• the magnetic disk 10 had passed 600,000 times and passed. Also, after the LUL test, the magnetic disk 10 was taken out and inspected, but no abnormalities such as scratches or dirt were detected. No precipitation of alkali metal components was observed.
• Comparative Example 1 is the glass of Example 5 described in JP-A-2001-1236634, and Comparative Example 2 is JP-A-11-1232627.
• the glass of Comparative Example 1 described in the gazette and Comparative Example 3 are the glass of Comparative Example 2 described in JP-A-11 314931.
• the glass of Comparative Example 1 did not contain ZrO, HfO, Nb 0, Ta 0, La 0, Y 0, and TiO, the chemical durability, particularly alkali resistance, was not sufficient.
• the amount of Ca 0 is less than the amount of MgO.
• FIG. 1 is a diagram showing an example of the configuration of a magnetic disk according to an embodiment of the present invention.
• FIG. 2 is an explanatory diagram of a method for measuring bending strength.

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